List for events included an editing button to mark the attendees as "attended" in the Report>Events tab. The checklist does not update once the attended box is clicked to must find the list again and go candidate by candidate and mark the checklist item as complete.
When I go into an "Event" through the candidate's Record, there is a checkbox for "attended," and when it is selected, it does update the checklist. Are you marking the "Checklist Status" as "Completed" through the same part of the page?